The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A thrust reverser of an aircraft engine nacelle is constructed with two annular panels, hinged by an aligned generatrix. The two panels have to be open during maintenance operations which may in particular be carried out in the open air. The large size of the cowls, their mass and their wind resistance involve handling forces which impose a mechanized opening, in particular by means of fluid jacks, most often hydraulic jacks.
Moreover, it is known that the cowls of the thrust reverser are fitted with locks so that, in operation, the nacelle remains closed. Hence, there exists a maintenance procedure which first imposes the deactivation of the closing locks of the thrust reverser cowls. Then a system for lifting the cowls by means of fluid jacks is controlled by the maintenance operator, so that the unlocked cowls rise to allow the access to the inside of the nacelle and/or of the turbojet engine itself.
However, a problem arises in case the operator omits to unlock the cowls. Because of the resistant forces, the jacks of the cowls lifting system are high-powered. As a result, if the locks have not been released, considerable forces are applied, resulting in damages of the cell.
In order to avoid these destructions, the mechanical portions that are subjected to the forces of the lifting system when the locks have inadvertently been left closed by the maintenance operator is oversized. However, such an oversizing induces in particular an increase of the mass of the nacelle, which is generally to be avoided in the aeronautical field.
Moreover, double-rod jacks can be used when the stroke of the jack is particularly long, which is the case for the opening of the cowls of the thrust reverser in a turbojet engine nacelle. Indeed, the external rod is provided by construction with a piston having a wider surface than the piston of the internal rod, since the latter has to slide inside the external rod at a second phase during the extension of the jack. As a result, the force exerted by the jack is higher by construction, at start-up of the jack at the beginning of its extension, than in the second portion of its extension, and this in the ratio of the surfaces of the pistons.